Propagating a Flow Policy by Control Packet in a Software Defined Network (SDN) Based Network

ABSTRACT

Propagating a flow policy within a software defined network (SDN) includes sending a route path request for a flow from a first forwarding node to an SDN controller of the SDN, receiving route path information specifying a route path for the flow from the SDN controller, and generating, using a processor of the first forwarding node, a control packet including the route path. The control packet is communicated from the first forwarding node to a second forwarding node.

BACKGROUND

A software-defined network (SDN) is an adaptable architecture for anetwork in which data routing decisions are decoupled from theparticular network nodes that perform the data transfers. The networknodes of the SDN responsible for making decisions about data routingform the “control plane.” The network nodes of the SDN responsible forforwarding the data form the “data plane.” An abstraction layer istypically included through which the SDN may be administered. Theabstraction layer hides lower level functionality and details of theunderlying network infrastructure. As such, SDNs are highly adaptable.For example, a network administrator may directly program aspects of theSDN including, but not limited to, network control, networkconfiguration, and otherwise centrally manage the SDN.

An SDN controller is the network node tasked with determining a routepath for data packets of a “flow.” The SDN controller is part of thecontrol plane of the SDN. The route path determined by the SDNcontroller specifies the particular network nodes and ordering of suchnetwork nodes through which data packets of a given flow will pass whencommunicated from a start node to an end node of the flow. The SDNcontroller is tasked with communicating the route path for the flow toeach of the network nodes of the route path. As such, controlinformation is kept within the control plane as a series ofcommunications that occur between the SDN controller and each networknode of the route path for the flow. Responsive to receiving route pathinformation for a flow from the SDN controller, each recipient networknode updates an internal flow table with the instructions received fromthe SDN controller. The instructions specify how the recipient networknodes are to process data packets belonging to the flow.

When the start node receives instructions from the controller, the startnode begins sending data packets of the flow over the data plane of theSDN to the next network node specified in the route path. In general,control plane communications refer to the exchange of controlinformation between the SDN controller and a data forwarding node,between the SDN controller and a start node, or between the SDNcontroller and the end node. Data plane communications refer to theexchange of data for a flow between start node and a forwarding node,between two forwarding nodes, or between a forwarding node and the endnode.

In some cases, data packets of the flow may be received by a networknode, e.g., a forwarding node, prior to that network node receivinginstructions from the SDN controller indicating how to process the datapackets. Any of a variety of different errors and/or delays may occur insuch a situation including, for example, data packets arriving at theend node out of order. The SDN architecture does not guaranteeconsistent handling of data packets belonging to a same flow.

SUMMARY

In one aspect, a method includes receiving, from a first forwarding nodeof a software defined network (SDN), a route path request for a flowand, responsive to the route path request, determining route pathinformation specifying a route path for the flow using a processor of anSDN controller. The method further includes communicating the route pathinformation from the SDN controller only to the first forwarding node.

In another aspect, a method includes sending a route path request for aflow from a first forwarding node to an SDN controller of an SDN,receiving route path information specifying a route path for the flowfrom the SDN controller, and generating, using a processor of the firstforwarding node, a control packet specifying the route path. The methodfurther includes communicating the control packet from the firstforwarding node to a second forwarding node.

In another aspect, a system includes a processor programmed to initiateexecutable operations. The executable operations include sending a routepath request for a flow from a first forwarding node to an SDNcontroller of an SDN, receiving route path information specifying aroute path for the flow from the SDN controller, and generating acontrol packet specifying the route path. The executable operations alsoinclude communicating the control packet from the first forwarding nodeto a second forwarding node.

In still another aspect, a computer program product includes a computerreadable storage medium having program code stored thereon. The programcode is executable by a processor to perform a method. The methodincludes sending a route path request for a flow from a first forwardingnode to an SDN controller of an SDN using a processor of the firstforwarding node, receiving route path information specifying a routepath for the flow from the SDN controller using the processor of thefirst forwarding node, and generating a control packet specifying theroute path using the processor of the first forwarding node. The methodfurther includes communicating the control packet from the firstforwarding node to a second forwarding node using the processor of thefirst forwarding node.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of a communicationsystem.

FIG. 2 is a block diagram illustrating an exemplary architecture for anetwork node.

FIG. 3 is a message flow diagram illustrating an exemplary use of acontrol packet for establishing a route path for a flow according to aflow policy within a software defined network (SDN).

FIGS. 4A and 4B are block diagrams illustrating exemplary controlpackets.

FIG. 5 is a flow chart illustrating an exemplary method of propagating aflow policy within an SDN.

FIG. 6 is a flow chart illustrating another exemplary method ofpropagating a flow policy within an SDN.

DETAILED DESCRIPTION

While the disclosure concludes with claims defining novel features, itis believed that the various features described herein will be betterunderstood from a consideration of the description in conjunction withthe drawings. The process(es), machine(s), manufacture(s) and anyvariations thereof described within this disclosure are provided forpurposes of illustration. Any specific structural and functional detailsdescribed are not to be interpreted as limiting, but merely as a basisfor the claims and as a representative basis for teaching one skilled inthe art to variously employ the features described in virtually anyappropriately detailed structure. Further, the terms and phrases usedwithin this disclosure are not intended to be limiting, but rather toprovide an understandable description of the features described.

This disclosure relates to software defined networks (SDNs) and, moreparticularly, to propagating a flow policy within an SDN. In accordancewith the inventive arrangements disclosed herein, a flow policy ispropagated and/or established using a control packet. A start nodebegins a flow directed to an end node. In doing so, the start nodeinitiates the flow by communicating with a network node, referred to asa forwarding node, of the SDN. The forwarding node, in turn, sends aroute path request for the flow to an SDN controller. The SDN controllerdetermines a route path for the flow and sends the route path to theforwarding node. The forwarding node generates a control packetincluding the route path and communicates the control packet to a nextforwarding node specified by the route path. The control packet, whichincludes and/or specifies the route path, is communicated from theforwarding node along the route path through the data plane of the SDNto each of the other forwarding nodes specified by the route path. Eachforwarding node that receives the control packet updates the flow tablestored therein in accordance the received control packet.

The forwarding node sends the control packet to the next forwarding nodeprior to sending any other data packet of the flow, e.g., data packets.Accordingly, each of the forwarding nodes of the route path is able toupdate the flow table stored therein with instructions dictating how toprocess received data packets for the flow. The instructions areguaranteed to be received by the various forwarding nodes of the routepath prior to any data packets of the flow. As such, per-flowconsistency is guaranteed and out of order data packets for the flow areavoided. Further details are described below with reference to thedrawings.

For purposes of simplicity and clarity of illustration, elements shownin the figures have not necessarily been drawn to scale. For example,the dimensions of some of the elements may be exaggerated relative toother elements for clarity. Further, where considered appropriate,reference numbers are repeated among the figures to indicatecorresponding, analogous, or like features.

FIG. 1 is a block diagram illustrating an exemplary communication system100. Communication system 100 is a networked system. In one aspect,communication system 100 is implemented as an SDN. Communication system100 includes a plurality of network nodes communicatively linked by anetwork 105. The network nodes include an SDN controller 110, a startnode 115, forwarding nodes 120, 125, and 130, and an end node 135.

Network 105 is the medium used to provide communication links betweenthe various network nodes connected together within communication system100. Network 105 may include connections, such as wire, wirelesscommunication links, or fiber optic cables. Network 105 may beimplemented as, or include, any of a variety of different communicationtechnologies such as a Wide Area Network (WAN), a Local Area Network(LAN), a wireless network, a mobile network, a Virtual Private Network(VPN), the Internet, the Public Switched Telephone Network (PSTN), orthe like.

In general, each network node may represent a data processing systemsuch as a switch, a router, a computer, or the like. SDN controller 110,for example, may be implemented as a server. Start node 115 and end node135 may be implemented as computing systems, mobile computing and/orcommunication systems, or the like. For example, start node 115 and endnode 135 each may be implemented as a client system that communicateusing a flow. Forwarding nodes 120, 125, and 130 each may be implementedas a switch, a router, a server, or the like. In one aspect, one or moreof start node 115, end node 135, or forwarding nodes 120, 125, and/or130 may be implemented as virtual machines executing within a host dataprocessing system or two or more different host data processing systems.Any network node that is part of a route path and not an SDN controller,not a start node that initiates a flow, and not an end node that is theendpoint of the flow is considered a forwarding node.

For purposes of discussion and illustration, start node 115 iscommunicatively linked to forwarding node 120. Similarly, end node 135is communicatively linked to forwarding node 130. In this regard,forwarding node 120 provides start node 115 with access to network 105.Similarly, forwarding node 130 provides end node 135 with access tonetwork 105.

In operation, start node 115, e.g., a client system, initiates a flow toend node 135. In general, a “flow” is a conversation and/or exchange ofdata between two endpoints such as start node 115 and end node 135. Eachpair of endpoints may be engaged in one or more different and activeflows. As defined within this disclosure, a “flow” means one or morepackets having a same flow identifier. The flow identifier typically isspecified in a header portion of a packet by the communicatingendpoints. The particular data items used to form the flow identifiermay vary across devices, network technologies, according to desiredgranularity, and/or the like. In illustration, a flow identifier havingcoarse granularity may utilize an address of the sender and an addressof the receiver. For example, the flow identifier may be a combinationof the Internet Protocol (IP) address for start node 115 and the IPaddress for end node 135. In another illustration, a flow identifierwith finer granularity may include more than one header such as a TCP/IP5-tupple including the MAC addresses of the start and end nodes, thesource and endpoint IP addresses, protocol used, and port information.

Start node 115 initiates a flow directed to end node 135 bycommunicating with forwarding node 120. For example, start node 115communicates one or more of data packets 155 to forwarding node 120.Responsive to start node 115 initiating the flow, forwarding node 120communicates a route path request 140 for the flow to SDN controller110. Route path request 140 specifies start node 115 and end node 135.In addition, route path request 140 may include one or more otherattributes.

In one aspect, communication system 100 and, more particularly, the SDN,may provide additional services beyond delivery of packets from startnode 115 to end node 135. These additional, or more advanced, servicesmay include, but are not limited to, Quality of Service (QoS),resiliency, security, multipath, other policy attributes and/or thelike. These advanced services may be implemented within, or by, SDNcontroller 105 and/or forwarding nodes 120, 125, and/or 130. Start node115, in initiating the flow with forwarding node 120, may request one ormore of such services to be used for the flow. Accordingly, forwardingnode 120 may include within route path request 140 one or moreattributes indicating the particular services to be used for the flow asrequested by start node 115.

SDN controller 110, responsive to receiving route path request 140,determines route path information 145 for the flow. Route pathinformation 145 includes a route path. The route path specifies anordered set of one or more network nodes, that each data packet of theflow will travel in moving from start node 115 to end node 135. Moreparticularly, SDN controller 110 determines one or more forwardingnodes, i.e., an ordered set of forwarding nodes, through which datapackets 155 of the flow will travel in order to move from start node 115to end node 135. In this example, a route path included in route pathinformation 145 specifies start node 115, forwarding node 120,forwarding node 125, and forwarding node 130 leading to end node 135.SDN controller 110 sends route path information 145 to forwarding node120. Thus, in this example, route path information 145 specifies thatthe flow will travel from start node 115 to forwarding node 120, toforwarding node 125, to forwarding node 130, and on to end node 135.

In another aspect, SDN controller 110 may determine any servicesspecified by route path request 140. In that case, SDN controller 110includes any attributes and/or instructions within route pathinformation 145 that are needed to direct forwarding nodes 120, 125, and130 of the route path to implement the requested services. As such, ifsupported, route path information 145 may specify the advanced servicesto be used by forwarding nodes 120, 125, and/or 130 in processing theflow. For example, route path information 145 may include instructionsfor forwarding nodes to perform operations such as rewriting, modifying,and/or augmenting data packet headers to specify fields that may beconsumed or used by one or more other forwarding nodes of the routepath, matching instructions to be performed against the fields in thedata packet headers for forwarding nodes of the route path, instructionsfor updating internal flow tables of the forwarding nodes of the routepath, and/or the like.

Unlike conventional SDN architectures, SDN controller 110 does notcommunicate route path information 145 relating to the flow initiated bystart node 115 to any forwarding node other than forwarding node 120.For example, SDN controller 110 does not communicate route pathinformation 145 to forwarding node 125 or to forwarding node 130 whensetting up the flow. Similarly, SDN controller 110 does not communicateroute path information 145 to start node 115 or to end node 135. Asillustrated in FIG. 1, SDN controller 110 only provides route pathinformation 145 to the particular network node that issued route pathrequest 140, which is forwarding node 120 in this example. In somecases, however, SDN controller 110 may communicate with a particulartype of network node that is capable of modifying the route path as willbe described in further detail within this specification.

Forwarding node 120, responsive to receiving route path 145 from SDNcontroller 110, generates control packet 150-1. Control packet 150-1includes, or specifies, at least a portion of route path information 145or a derivative or modification thereof. For example, control packet150-1 may specify the route path, i.e., the ordered set of forwardingnodes, any attributes for advanced services to be performed,instructions for updating flow tables, instructions for processingpackets and/or header information as previously described, etc. In oneaspect, control packet 150-1 includes route path information 145 withina payload portion of control packet 150-1. In another aspect, controlpacket 150-1 includes route path information 145 in an encapsulated formallowing each forwarding node to read and/or remove needed informationfrom the control packet and/or remove an encapsulation layer prior tosending the control packet, or a modified version thereof, to a nextnetwork node of the route path.

Forwarding node 120 updates an internally stored flow table according toroute path information 145 so that other packets of the flow will besent to the next node in the route path. In this example, the next nodeof the route path is forwarding node 125. Forwarding node 120 furthercommunicates control packet 150-1 to forwarding node 125. Forwardingnode 125 evaluates control packet 150-1 and updates an internally storedflow table based upon the route path information 145 specified bycontrol packet 150-1. Forwarding node 125, as a result of updating theinternally stored flow table, is configured to forward packets of theflow to the next network node of the route path, which is forwardingnode 130. Forwarding node 125 updates and/or modifies control packet150-1, thereby generating control packet 150-2. Forwarding node 125communicates, or forwards, control packet 150-2 to forwarding node 130.As noted, in one aspect, only the residual or remaining nodes of theroute path may be included or specified by control packet 150-2 asopposed to portions of the route path already traversed such as startnode 115 and/or forwarding node 120.

Forwarding node 130 evaluates control packet 150-2 and updates aninternally stored flow table based upon the received route pathspecified by control packet 150-2. Forwarding node 130 determines thatno further forwarding nodes are specified for the route path and, assuch, does not send a control packet to end node 135. Forwarding node130, however, is programmed, or configured, to send data packets 155 ofthe flow to end node 135.

Subsequent to forwarding node 120 sending control packet 150-1 toforwarding node 125, forwarding node 120 may begin sending one or moreof data packets 155 of the flow as received from start node 115. Datapackets 155 of the flow, however, are not sent by forwarding node 120until after control packet 150-1 is sent. As described in further detailwithin this disclosure, control packet 150-1 is sent over the data planeof the SDN. Sending control packet 150-1 over the data plane prior tosending any data packets of the flow ensures that consistency inapplication of any policy for data packets 155 of the flow is observed.In particular, control packets propagate through the forwarding nodespreceding any data packets of the flow. As illustrated in FIG. 1, datapackets 155 are sent from start node 115 to end node 135 via theestablished route path.

Thus, data packets 155 travel from start node 115, to forwarding node120, to forwarding node 125, to forwarding node 130, through to end node135. Each of forwarding nodes 120, 125, and 130 processes data packets155 in accordance with the particular instructions for the flowcorresponding to that forwarding node as specified by received routepath information 145. Forwarding node 120 receives route pathinformation 145 directly from SDN controller 110. Forwarding node 125receives route path information 145 from forwarding node 120 via controlpacket 150-1. Forwarding node 130 receives route path information 145from forwarding node 125 via control packet 150-2.

Communication system 100 is provided for purposes of illustration only.A communication system may include additional network nodes, whetherswitches, routers, data processing systems, virtual machines, or thelike, or fewer of network nodes. Further, while the example of FIG. 1has been described with the control packet including route pathinformation, in another example, the control packet may also includeactual data of the flow.

FIG. 2 is a block diagram illustrating an exemplary architecture 200 fora network node. Architecture 200 may be used to implement any of avariety of different network nodes as described with reference toFIG. 1. For example, architecture 200 may be used to implement a router,a switch, a computer, including a client, a server, or the like. Moreparticularly, architecture 200 illustrated in FIG. 2 may be used toimplement SDN controller 110, start node 115, end node 135, or any ofthe various forwarding nodes described with reference to FIG. 1.

Architecture 200 includes at least one processor (e.g., a centralprocessing unit) 205 coupled to memory elements 210 through a system bus215 or other suitable circuitry. As such, a network node havingarchitecture 200 can store program code within memory elements 210.Processor 205 executes the program code accessed from memory elements210 via system bus 215 or the other suitable circuitry.

In one aspect, architecture 200 is implemented as a programmable dataprocessing apparatus that is suitable for storing and/or executingprogram code. It should be appreciated, however, that architecture 200can be used to implement any network node and/or system including aprocessor and memory that is capable of performing and/or initiating thefunctions and/or operations described within this disclosure. Further,architecture 200 can be used to implement a network node and/or systemhaving any of a variety of different form factors.

Memory elements 210 include one or more physical memory devices such as,for example, local memory 220 and one or more bulk storage devices 225.Local memory 220 refers to random access memory (RAM) or othernon-persistent memory device(s) generally used during actual executionof the program code. Bulk storage device(s) 225 can be implemented as ahard disk drive (HDD), a solid state drive (SSD), or other persistentdata storage device. Architecture 200 also can include one or more cachememories (not shown) that provide temporary storage of at least someprogram code in order to reduce the number of times program code must beretrieved from bulk storage device 225 during execution. It should beappreciated that memory elements 210 may include any of a variety ofdifferent computer readable storage media.

Input/output (I/O) devices such as a keyboard 230, a display device 235,and a pointing device 240 optionally can be coupled to architecture 200.The I/O devices can be coupled to architecture 200 either directly orthrough intervening I/O controllers. One or more network adapters 245also can be coupled to architecture 200 to enable a network node usingarchitecture 200 to become coupled to other network nodes such as othercomputer systems, remote printers, and/or remote storage devices throughintervening private or public networks. Modems, cable modems, wirelesstransceivers, and Ethernet cards are examples of different types ofnetwork adapters 245 that can be used with architecture 200.

As pictured in FIG. 2, memory elements 210 can store an SDN module 250.SDN module 250, being implemented in the form of executable programcode, is executed by a network node using architecture 200 and, as such,is considered an integrated part of any such system. In the case wherearchitecture 200 is used to implement an SDN controller, SDN module 250includes the program instructions that, when executed, cause the networknode to perform the various operations described within this disclosurefor an SDN controller. In the case where architecture 200 is used toimplement a start node or an end node, e.g., a client, SDN module 250includes the program instructions that when executed, cause the networknode to perform the various operations described within this disclosurefor a start node and/or an end node. In the case where architecture 200is used to implement a forwarding node, SDN module 250 includes theprogram instructions that when executed, cause the network node toperform the various operations described within this disclosure for aforwarding node.

Forwarding nodes store a flow table (not shown) within memory elements210. A forwarding node using architecture 200, under control of SDNmodule 250, updates the flow table in accordance with informationspecified within a received control packet from another forwarding nodeor in accordance with route path information received directly from theSDN controller as described within this disclosure. For example, anexisting entry in the flow table corresponding to the flow may beupdated or a new entry in the flow table for the flow may be created. Itshould be appreciated that SDN module 250, including any parametersand/or attributes utilized by SDN module 250 such as route pathinformation, a control packet, and/or a flow table, are functional datastructures that impart functionality when employed as part of a networknode and/or system utilizing architecture 200.

FIG. 3 is a message flow diagram illustrating an exemplary use of acontrol packet for establishing a route path for a flow according to aflow policy within an SDN. FIG. 3 illustrates messaging that occursbetween network nodes of an SDN in establishing a flow and variousoperations performed by the network nodes. FIG. 3 begins in a statewhere start node 115 initiates a flow to end node 135 by sendingcommunication 305 to forwarding node 120. In one aspect, communication305 specifies start node 115, end node 135, and/or data packets 155.Communication 305 further may include attributes requesting one or moreservices for the flow. As discussed, forwarding node 120 may providestart node 115 with access to network communications.

Responsive to communication 305, forwarding node 120 sends route pathrequest 140 for the flow to SDN controller 110. Routing path request 140is sent over the control plane of the SDN. Route path request 140specifies start node 115 and end node 135, e.g., IP addresses for thestart and end nodes for the flow. Further, route path request 140 mayinclude one or more attributes relating to the services to be applied tothe flow as requested by start node 115.

SDN controller 110 receives route path request 140. Responsive toreceiving route path request 140, SDN controller 110 determines routepath information 145 for the flow in block 310. Route path information145, as determined by SDN controller 110, includes or specifies startnode 110, end node 135, one or more forwarding nodes such as forwardingnodes 120, 125, and 130, and an ordering of the network nodes formingthe route path. As part of route path information 145, SDN controller110 further may include one or more attributes and/or instructions forthe flow. Attributes and/or instructions may be specified within routepath information 145 on a per-forwarding node basis. SDN controller 110sends route path 145 to forwarding node 120. SDN controller 110 sendsroute path information 145 over the control plane of the SDN directly toforwarding node 120.

Responsive to receiving route path information 145, forwarding node 120generates control packet 150-1 in block 315. In general, forwarding node120 sends control packet 150-1 along the route path determined by SDNcontroller 110. One or more control packets specifying route pathinformation 145, or a derivative thereof, traverse the route path overthe data plane of the SDN. In one aspect, control packets such ascontrol packet 150-1 and/or 150-2 include the same header or headerinformation that will be included in data packets 155 for the flow. Assuch, the decisions of any forwarding nodes of the route path having anability to make a decision whether to pass a data packet 155 of theflow, block a data packet 155 of the flow, or divert a data packet 155of the flow based upon header information may be observed in how thecontrol packets are handled and/or processed.

In block 320, forwarding node 120 updates a flow table stored in memorytherein. The flow table stored within forwarding node 120 is updatedwith any instructions included in route path 145 that indicate howforwarding node 120 is to process data packets 155 of the flow. As usedherein, the phrases “updating the flow table,” “update the flow table,”or variants thereof, as performed by a forwarding node, refer to aprocess performed responsive to receiving a control packet and/or routepath information 145. Updating means that the forwarding node searchesfor an entry in the flow table that matches the received control packet.

For example, the forwarding node determines a flow identifier from thereceived control packet or from received route path information 145. Theforwarding node searches for an entry in the flow table having amatching flow identifier. If the forwarding node locates a matchingentry, the forwarding node updates the matching entry with anyinstructions of the control packet for the forwarding node. Theinstructions dictate how the forwarding node handles, e.g., routes, datapackets 155 for the flow. For example, such instructions dictate thatforwarding node 120 is to forward data packets 155 to forwarding node130 using any applicable services. If the forwarding node is unable tolocate a matching entry, the forwarding node adds or creates an entry inthe flow table that includes the instructions for the forwarding node asspecified by the received control packet and/or route path information145 for the flow.

With control packet 150-1 having been generated, forwarding node 120communicates control packet 150-1 to a next network node of the routepath. In this example, the next network node of the route path isforwarding node 125. Responsive to receiving control packet 150-1,forwarding node 125 performs one or more operations. In block 325,forwarding node 125 updates a flow table stored in memory therein asdescribed with reference to forwarding node 120. The flow table storedwithin forwarding node 125 is updated with any instructions included inthe route path of control packet 150-1 that indicate how forwarding node125 is to process data packets 155 of the flow. For example, the flowtable of forwarding node 125 is updated to indicate that data packets155 are to be forwarded to forwarding node 130 using any applicableservices.

In block 330, forwarding node 125 modifies control packet 150-1. Forexample, forwarding node 125 updates header information of controlpacket 150-1 to indicate a next network node of the route path. Themodified version of control packet 150-1 is control packet 150-2. Inthis example, the next network node in the route path pictured isforwarding node 130. Forwarding node 125 communicates control packet150-2 to forwarding node 130.

Responsive to receiving control packet 150-2, forwarding node 130performs one or more operations. In block 335, forwarding node 130updates a flow table stored in memory therein. The flow table storedwithin forwarding node 130 is updated with any instructions included inthe route path of control packet 150-2 that indicate how forwarding node130 is to process data packets 155 of the flow. For example, forwardingnode 130 updates the internal flow table with instructions dictatingthat data packets 155 are to be forwarded to end node 135.

Forwarding node 120 sends data packets 155 of the flow subsequent tosending control packet 150-1 to forwarding node 125. While data packets155 are shown to be sent from forwarding node 120 after control packetspropagate to forwarding node 130, the ordering of communications shownis not intended to be limiting. Still, no data packet 155 of the flow issent from forwarding node 120 until after the sending of control packet150-1. For example, forwarding node 120 may send data packets 155immediately after sending control packet 150-1. In another example,forwarding node 120 may send data packets 155 responsive to the passingof a predetermined amount of time after sending control packet 150-1.

FIGS. 4A and 4B are block diagrams illustrating exemplary controlpackets. In the examples presented in FIGS. 4A and 4B, the controlpackets are implemented or formatted as User Datagram Protocol (UDP)packets. It should be appreciated that any of a variety of differentpacket formats and/or protocols may be used. UDP packets are only usedfor purposes of illustration and not limitation. Further, FIGS. 4A and4B illustrate examples in which the route path is specified in thepayload portion of each control packet. As noted, however, the payloadportion may include data for the flow, instructions, and/or otherattributes for the flow. Further, the route path may be specified by, orwithin, the control packet using encapsulation rather than beingincluded within the payload portion of the control packet.

FIG. 4A is an exemplary illustration of control packet 150-1 asgenerated by forwarding node 120. Control packet 150-1 includes anEthernet header portion, an IP header portion, a transport headerportion, and a payload portion. The IP header portion specifies thesource IP address (Src IP) of the network node from which control packet150-1 is sent and the destination IP address (Dst IP) of the networknode to which control packet 150-1 is sent. The source IP address forcontrol packet 150-1 is the IP address of forwarding node 120 (IP₁). Thedestination IP address of control packet 150-1 is the IP address offorwarding node 125 (IP₂). The transport header specifies the sourceport and the destination port to be used. In this example, controlpacket 150-1 is identified by a unique UDP port number of 40. Payloadportion of control packet 150-1 includes an ordered list of the networknodes forming the route path as determined by the SDN controller.

Forwarding node 125 examines the payload portion of control packet150-1. Forwarding node 125 updates the flow table stored therein. Asnoted, forwarding node 125 searches for an entry in the flow tablehaving a flow identifier matching the flow identifier of control packet150-1. If forwarding node 125 locates a matching entry in the flowtable, forwarding node 125 updates the entry with any instructionsincluding the next network node in the route path that may be specifiedwithin control packet 150-1. If forwarding node 125 is unable to locatea matching entry in the flow table, forwarding node 125 creates an entryin the flow table for the flow. The instructions for the flow, asobtained from control packet 150-1, are stored in the flow table entrythat is created.

Forwarding node 125 identifies the next node of the route path from thepayload portion of control packet 150-1. Forwarding node 125 modifiescontrol packet 150-1, thereby generating control packet 150-2 of FIG.4B. As pictured in FIG. 4B, forwarding node 125 has updated the sourceIP address and the destination IP address of control packet 150-2. Moreparticularly, forwarding node 120 has updated the source IP address toIP₂ and the destination IP address to IP₃, corresponding to forwardingnode 125 and forwarding node 130, respectively. Forwarding node 125sends control packet 150-2 to forwarding node 130.

Responsive to receiving control packet 150-2, forwarding node 130examines the payload portion of control packet 150-2. Forwarding node130 updates the flow table stored therein as previously described.Forwarding node 130 also identifies the next node of the route path fromthe payload portion of control packet 150-2. Forwarding node 130determines that the next network node is end node 135. As such,forwarding node 130 does not modify and/or send control information toend node 135.

In the case where control packet 150-2 includes data within the payloadportion, however, forwarding node 130 may generate a data packet havingthe data included therein which may be sent to end node 135. In anotheraspect, forwarding node 130 may update the IP header of control packet150-2 and forward the modified version of control packet 150-2 to endnode 135 so that end node 135 may extract the data.

Accordingly, with control packets traversing the route path asdescribed, each forwarding node is configured with the appropriateinstructions for handling data packets of the flow. Each such datapacket will have a flow identifier that may be matched to theinstructions stored within an entry in the flow table of each respectiveforwarding node.

Though not illustrated in FIG. 4, in another aspect, the payload of thecontrol packet may include a hop counter data field. The hop counterdata field may be used by a forwarding node to quickly determine theoffset within the control packet and/or payload of the control packet todetermine the next network node of the route path. Each forwarding node,as part of modifying the IP header information, would also update thehop counter data field prior to sending the modified control packet tothe next network node.

In still another aspect, forwarding nodes may be configured to strip orremove any information from the control packet that was utilized by aprior forwarding node or a prior network node. In that case, eachforwarding node would remove those network nodes, or hops, from thepayload portion of the control packet that were visited. As such, uponreceipt of a control packet, each forwarding node need only check asame, fixed location within the packet to determine the next networknode of the route path. For example, control packet 150-3, being sentfrom forwarding node 125 to forwarding node 130, would have a payloadwith only end node 135 specified for the route path since each othernetwork node was traversed.

In some cases, the flow policy propagation techniques described withinthis disclosure may be augmented to accommodate network nodes having thecapability to change the route path of the flow referred to as a“decision making network node.” A firewall is an example of a decisionmaking network node. A firewall, for example, may decide that a certainflow and/or packet of a flow should be forwarded through an intrusiondetection system, blocked, or otherwise diverted from the route path. Insuch cases, the SDN controller may determine a conservative route paththat avoids the decision making network node or provide a route path upto, and ending at, the decision making network node. In each case,forwarding nodes up to the decision making network node are updated. Thedecision making network node may modify the route path specified withinthe existing control packet that is received or request a remainingportion of a path from the SDN controller, where the remaining portionof the route path is from the decision making network node to the endnode.

The example provided above for a decision making network node isapplicable to situations where the decision making network node makesdecisions based upon n-tuple information of the control packet, where“n” is an integer value, e.g., 5. In cases where the decision makingnetwork node is able to inspect the payload of the control packet, thedecision making network node also must be able to read and/or accessheader information for the packet. In such cases, the control packet maybe augmented so that header information of the control packet is alsoincluded or incorporated into the payload portion of the control packetand, thereby available for inspection from a decision making networknode configured to inspect payloads.

FIG. 5 is a flow chart illustrating an exemplary method 500 ofpropagating a flow policy in an SDN. Method 500 may be implemented bythe SDN controller as described within this disclosure. In block 505,the SDN controller receives a route path request for a flow from aforwarding node of the SDN. The forwarding node from which the routepath request is received may be a first forwarding node, or oneconnected to a client that is initiating a flow to another client. Theroute path request may specify the start node and the end node for theflow. In another aspect, the route path request may specify one or morerequested services to be applied or used for the flow.

In block 510, responsive to the route path request, the SDN controllerdetermines route path information for the flow. The route pathinformation may specify the start node, the end node, and one or moreforwarding nodes. The route path information further may specifyinformation to be used by the forwarding nodes in processing the flowsuch as one or more services to be applied to packets of the flow and/orinstructions for handling packets of the flow. The route pathinformation may specify the aforementioned data on a per-forwarding nodebasis.

In block 515, the SDN controller communicates the route path informationto the forwarding node. The route path information is communicated onlyto the forwarding node that issued the route path request. The routepath information is not sent from the SDN controller directly to anyother forwarding node of the route path. Rather, the route pathinformation propagates as one or more control packets from oneforwarding node to the next in accordance with the ordered list offorwarding nodes specified therein.

FIG. 6 is a flow chart illustrating another exemplary method 600 ofpropagating a flow policy in an SDN. Method 600 may be implemented by aforwarding node as described within this disclosure. In block 605, theforwarding node sends a route path request for a flow to the SDNcontroller of an SDN. As noted, the forwarding node may send the routepath request responsive to a client initiating a flow. In block 610, theforwarding node receives route path information for the flow from theSDN controller. In block 615, the forwarding node generates a controlpacket specifying the route path. In another aspect, one or more itemsor the entirety of the route path information is included or specifiedby the control packet generated by the forwarding node.

In block 620, the forwarding node updates an internally stored flowtable. The flow table is used to store entries indicating how to processdifferent flows. For example, each entry corresponds to one flow thathis being handled or processed by the forwarding node. Responsive toreceiving the route path information, the forwarding node determines theflow identifier from the received route path information. The forwardingnode determines whether the internally stored flow table includes anentry having a flow identifier matching the flow identifier determinedfrom the received route path information. If so, the matching entry isupdated in accordance with the route path information for the forwardingnode. If not, an entry is created specifying route path information forthe forwarding node.

In block 625, the forwarding node communicates the control packet to thenext, e.g., or second, forwarding node in the route path. As discussed,responsive to receiving the control packet, the second forwarding nodeupdates the internally stored flow table. If a third forwarding nodebeyond the second forwarding node is specified by the route pathinformation, the second forwarding node modifies the control packet forsending to the third forwarding node. Forwarding nodes continue toupdate internal tables and communicate a control packet to the nextforwarding node until the last forwarding node of the route path isreached. After updating the flow table in each forwarding node asdescribed herein, each forwarding node of the route path is configuredto forward data packets from one endpoint of the flow to the other.

The inventive arrangements disclosed within this specification provideflow policy propagation techniques in which the flow table entries ofthe forwarding nodes along the route path of the flow are updated priorany of the forwarding nodes receiving data packets of the flow forprocessing. As such, per-flow consistency is guaranteed and out of orderdata packets for the flow are avoided. In addition, the control planeload is reduced since flow table entries are sent over the data plane asopposed to the control plane of the SDN. Further, the flow policypropagation technique(s) described within this disclosure guarantee thatonly necessary flow table entries are created in the forwarding nodesalong the route path of the flow that is computed.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes,”“including,” “comprises,” and/or “comprising,” when used in thisdisclosure, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Reference throughout this disclosure to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment described within this disclosure.Thus, appearances of the phrases “in one embodiment,” “in anembodiment,” and similar language throughout this disclosure may, but donot necessarily, all refer to the same embodiment.

The term “plurality,” as used herein, is defined as two or more thantwo. The term “another,” as used herein, is defined as at least a secondor more. The term “coupled,” as used herein, is defined as connected,whether directly without any intervening elements or indirectly with oneor more intervening elements, unless otherwise indicated. Two elementsalso can be coupled mechanically, electrically, or communicativelylinked through a communication channel, pathway, network, or system. Theterm “and/or” as used herein refers to and encompasses any and allpossible combinations of one or more of the associated listed items. Itwill also be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms, as these terms are only used to distinguishone element from another unless stated otherwise or the contextindicates otherwise. The term “if” may be construed to mean “when,”“upon,” “in response to [a stated condition or operation],” or“responsive to [a stated condition or operation]” depending on thecontext.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method, comprising: receiving, from a firstforwarding node of a software defined network, a route path request fora flow; responsive to the route path request, determining route pathinformation specifying a route path for the flow using a processor of asoftware defined network controller; and communicating the route pathinformation from the software defined network controller only to thefirst forwarding node.
 2. The method of claim 1, wherein the route pathrequest specifies a start node and an end node.
 3. The method of claim1, wherein the route path information further specifies a service to beapplied to the flow.
 4. The method of claim 1, wherein the firstforwarding node generates a control packet comprising the route path andcommunicates the control packet to a second forwarding node of the routepath.
 5. The method of claim 4, wherein the control packet iscommunicated from the first forwarding node to the second forwardingnode using a data plane of the software defined network withoutintervention from the software defined network controller.
 6. The methodof claim 5, wherein the first forwarding node sends the control packetto the second forwarding node prior to communicating any other packet ofthe flow to the second forwarding node.
 7. A method, comprising: sendinga route path request for a flow from a first forwarding node to asoftware defined network controller of a software defined network;receiving route path information specifying a route path for the flowfrom the software defined network controller; generating, using aprocessor of the first forwarding node, a control packet comprising theroute path; and communicating the control packet from the firstforwarding node to a second forwarding node.
 8. The method of claim 7,wherein the control packet is communicated from the first forwardingnode to the second forwarding node over a data plane of the softwaredefined network without intervention from the software defined networkcontroller.
 9. The method of claim 7, wherein the control packet is sentfrom the first forwarding node to the second forwarding node prior tocommunicating any other packet of the flow to the second forwardingnode.
 10. The method of claim 7, wherein the first forwarding nodecomprises a flow table and, responsive to receiving the route pathinformation, updates the flow table; and wherein the first forwardingnode processes a data packet of the flow according to the updated flowtable.
 11. A system, comprising: a processor programmed to initiateexecutable operations comprising: sending a route path request for aflow from a first forwarding node to a software defined networkcontroller of a software defined network; receiving route pathinformation specifying a route path for the flow from the softwaredefined network controller; generating a control packet comprising theroute path; and communicating the control packet from the firstforwarding node to a second forwarding node.
 12. The system of claim 11,wherein the control packet is communicated from the first forwardingnode to the second forwarding node over a data plane of the softwaredefined network without intervention from the software defined networkcontroller.
 13. The system of claim 11, wherein the control packet issent from the first forwarding node to the second forwarding node priorto communicating any other packet of the flow to the second forwardingnode.
 14. The system of claim 11, wherein the first forwarding nodecomprises a flow table and, responsive to receiving the route pathinformation, updates the flow table; and wherein the first forwardingnode processes a data packet of the flow according to the updated flowtable.
 15. A non-transitory computer program product comprising acomputer readable storage medium having program code stored thereon, theprogram code executable by a processor to perform a method comprising:sending a route path request for a flow from a first forwarding node toa software defined network controller of a software defined networkusing a processor of the first forwarding node; receiving route pathinformation specifying a route path for the flow from the softwaredefined network controller using the processor of the first forwardingnode; generating a control packet comprising the route path using theprocessor of the first forwarding node; and communicating the controlpacket from the first forwarding node to a second forwarding node usingthe processor of the first forwarding node.
 16. The computer programproduct of claim 15, wherein the control packet is communicated from thefirst forwarding node to the second forwarding node over a data plane ofthe software defined network without intervention from the softwaredefined network controller.
 17. The computer program product of claim15, wherein the control packet is sent from the first forwarding node tothe second forwarding node prior to communicating any other packet ofthe flow to the second forwarding node.
 18. The computer program productof claim 15, wherein the first forwarding node comprises a flow tableand, responsive to receiving the route path information, updates theflow table; and wherein the first forwarding node processes a datapacket of the flow according to the updated flow table.